But a lot of U.S. residents aren’t armed with accurate information to allow them to properly prepare for Zika’s arrival, said Gillian SteelFisher, deputy director of the Harvard Opinion Research Program at Harvard’s T.H. Chan School of Public Health in Boston.

The results of the poll show that people often don’t know how Zika spreads, or the effects it can have on human health, SteelFisher said.

“There are some important misconceptions about Zika virus,” SteelFisher said. “Some of those could prevent people at risk from taking steps to protect their pregnancies. And, then there’s the reverse problem, which is there are some misconceptions that could cause people to take unnecessary or inappropriate precautions.”

At this time, there has been no local transmission of Zika in the United States. But, about 273 residents have acquired Zika through travel to countries where the virus is active, primarily Latin America and the Caribbean, the U.S. Centers for Disease Control and Prevention (CDC) says.

The virus, which generally doesn’t cause serious illness in adults, has been associated with thousands of cases, mostly in Brazil, of a severe birth defect call microcephaly. Babies with microcephaly have abnormally small heads, and most wind up with stunted brain development, according to the CDC.

However, when SteelFisher and her colleagues surveyed people, including those in such households, they found that about 20 percent of Americans weren’t aware that Zika virus can be transmitted from mother to baby during pregnancy.

The researchers also found that:

About one in four isn’t aware of the association between Zika virus and the birth defect microcephaly.

One in five believes, incorrectly, that there is a vaccine to protect against Zika.

A quarter think individuals infected with Zika are “very likely” to show symptoms.

There is no vaccine or antiviral treatment for Zika, SteelFisher said. And, reports have shown that Zika can be spread from a man to a woman via sex, according to the CDC.

Most people with Zika don’t show any symptoms. Those who do have symptoms tend to have mild ones — fever, rash, joint pain, red eyes, muscle pain or headache, according to the CDC.

The misinformation that people showed in the poll means they may not take proper steps to avoid mosquito bites or mosquito-proof their property, SteelFisher said.

“Microcephaly is a major birth defect, and you want people who are pregnant or are considering it to have that information so they’ll be motivated to protect themselves,” SteelFisher said.

On the other hand, inaccurate perceptions can lead some people to become needlessly fearful of Zika, she added.

Nine out of 10 people accurately understand that Zika mainly spreads through mosquito bites, SteelFisher said.

But nearly a third of those surveyed also believe incorrectly that they can contract Zika from someone else’s cough or sneeze, the researchers found.

“That’s the way a lot of viruses are transmitted, but just not Zika virus,” SteelFisher said. “They think it’s like the flu or like a cold. That’s not how it’s passed.”

Zika is passed through mosquito bites, sexual transmission or blood transfusion, she said.

There’s also unnecessary concern that a Zika infection now will harm future pregnancies, the researchers said.

About four in 10 people surveyed mistakenly believe Zika will cause birth defects even after a woman has gotten over the virus, SteelFisher said.

“There’s no evidence that once an infection is over, Zika virus could affect a future pregnancy,” she said. “If the virus is cleared from your blood, there’s no risk to a future pregnancy. That’s where the evidence stands today.”

Dr. Amesh Adalja, a senior associate at the UPMC Center for Health Security in Baltimore, said these sort of misconceptions are common.

“Correcting mistaken conceptions of disease in the public is difficult in the best of times, but extremely daunting in the midst of an outbreak situation in which there is a large amount of sensationalistic media coverage,” Adalja said. “Public health officials must continuously repeat to the public what is definitely known about Zika, what isn’t known, and what questions about it need more research to answer.”

SteelFisher agreed. “I feel like there is an opportunity here,” she said. “Mosquito season hasn’t started in full this year, so we have an opportunity to reach people.”

The Harvard poll involved 1,275 adults, including 105 who live in households where someone is pregnant or considering getting pregnant in the next 12 months. It was conducted between March 2 and March 8, 2016.